Micropollutants that are present in surface water bodies have high risk for the environment. These toxic compounds originate from industrial and agricultural activities and activities of individuals. They include heavy metals and polycyclic aromatic hydrocarbons (PAHs) such as industrial chemicals, dyes, pesticides, pharmaceuticals, personal care products, and steroid hormones. Removing micropollutants from waste water helps to protect nature and the human population. Current waste water treatment plants (WWTPs) are not able to degrade these micropollutants effectively. They are therefore removed by reverse osmose filtration (RO) to produce drinking water. This results in a waste stream with a 3-5 fold higher concentration of micropollutants and ammonium. This concentrate is returned to WWTPs and finally, is returned to surface water bodies. Here, we aim to purify RO waste water from micropollutants using the mycelium of mushroom forming white rot fungi (WRFs).

WRF are main contributors of carbon cycling in nature by degrading the highly recalcitrant lignin in plant waste. Lignin, the second most abundant natural polymer after cellulose, consists of complex PAHs that are degraded by WRFs by secreting lignin oxidases (LO family) and lignin-degrading auxiliary enzymes (LDA family). These oxidizing enzymes can also degrade other PAHs, including micropollutants. Yet, it is not clear which individual enzymes are responsible for degradation of each PAH. Notably, WRF also adsorb and accumulate heavy metals. The resistance to these toxic compounds differs between species and the underlying mechanism(s) are poorly understood.

Apart from micropollutants, water needs to be purified from ammonium (NH4+). It promotes growth of algae and duckweed and thereby affects biodiversity. Moreover, NH4+ can dissociate in NH3 and H+. NH3 can be toxic for instance for fish. Since fungi can use ammonium as nitrogen source, detoxification of micropollutants can be combined with conversion of ammonium in biomass. This could thus be a positive side effect of the purification from micropollutants.

In this project, we will systematically assess the degrading and sorbing activities of micropollutants by mushroom forming WRFs and will for the first time study the molecular mechanisms that explain the differences in these activities between these fungi. Knowledge of these mechanisms will enable us to design a water purification system.

• prof. dr. H.A.B. (Han) Wösten

• prof.dr.ir. W.G.J. van der Meer